The present invention relates to an inkjet recording apparatus, and in particular, to an inkjet recording apparatus having a capping device to suction ink from a nozzle hole of printing head (hereinafter also called inkjet head) of inkjet recording apparatus.
In the inkjet recording apparatus, due to long period of nonuse, troubles such as clogging caused by increase of a viscosity of ink because of vaporization of moisture from a nozzle hole of the printing head, clogging of a nozzle by stuffing with paper dust and inability of ink ejection due to pressure loss of inner pressure caused by entering of air bubbles from the nozzle, occur. In addition, adhesion of unwanted ink on the surface of nozzle member results in causes to induce deflected ejection of ink and ink ejection failure.
Printing under such condition causes deterioration of outputted image, such as white spot and deep color spot on outputted image. Therefore, maintenance to recover from the status of pressure loss and clogging is needed.
As a maintenance method, there is disclosed a method to recover inability of ejection by covering the surface of nozzle member with a cap on a close contact basis, and by suctioning while the surface of nozzle member and the cap which are on close contact are partially released (for example, refer to Patent document 1).
There is further disclosed a method having a capping device to cover some nozzle holes in a plurality of nozzle holes and a suction device to suction ink from the aforesaid some nozzle holes through the capping device, or having a blocking device to block some nozzle holes in a plurality of nozzle holes and a pressure device to discharge ink from other nozzle holes than blocked nozzle holes (for example, Patent document 2).
(Patent Document 1) Japanese Registration Patent No. 3083409
(Patent Document 2) Japanese Registration Patent No. 2718724
In recent years, in inkjet recording apparatuses, the number of nozzle to eject ink has been increased due to improvement of printing speed. If inability of ejection occurs on these nozzles, it causes deterioration of output image.
In a recovering method according to Patent document 1 wherein a cap suctions to recover inability of ejection, as a recovering device, whole printing head has to be covered to recover only one nozzle in case of a large number of nozzles, resulting in ejection of a large amount of ink, for recovering one nozzle, and thereby, ink is wasted.
Also, due to downsizing of the printing head, the nozzle portion is integrated highly densely and manufacturing of the cap to suit a single nozzle is difficult, which results in a cost increase. Therefore, in actual suctioning is carried out including some neighborhood nozzles in place of a single nozzle. To cope with these problems, a cap covering a part of nozzle is invented in Patent document 2. However, according to the structure in Patent document 2, in case ink remaining at the portion where the cap and printing head contact each other at a rim of nozzle in the course of recovering action in a sequence where the cap is contacted, suctioned, maintained and released, deflective ejection of ink is caused, because of the structure of the cap.